Blown actions often are seen with pieces of brass that had been molten, then froze to the steel. Once high pressure gas is released into the bolt lug recess or the magazine well, it expands rapidly. It blows the receiver ring apart, which allows the barrel to move forward and the bolt to move back, which releases more gas which continues to expand and causes even greater damage.
OK. Sounds logical to me. But...
This scenario seems to assume that there is a pressure overcharge that causes the extreme flow of the brass, it's subsequent failure, release of gas, receiver failure...correct? This wouldn't happen otherwise with factory or other correctly designed loads- without a defect.
In the case of Mobuck's failure though (and other military actions) that fail when there is not an overpressure, what causes the receiver ring failure? Sorry- not trying to beat a dead horse here but still not following...
Are we to assume, that in order for that type of failure to occur-your scenario , or Mobuck's failure, there had to be something else "amiss"- perhaps an already stretched, or otherwise weak or defective casehead, or excessive headspace- that caused the sudden release of gas to blow apart the receiver?
To clarify (and guess I'm being a stupid PITA here), I am still trying to understand the role of the receiver ring, as relates to the overall ability of the action to withstand magnum chambering pressures. IOW, under normal circumstances, what loads are placed on the receiver ring- which would presumably be exceeded by a magnum cartridge for which it wasn't designed?
I inquired with Savage and Remington about using a "standard" magnum action, for a .338 LM. Both told me, the bolts / receivers were not designed for the bolt thrust generated by this cartridge. I get that- a sheared lug..but this is different.